JPH0971401A - Catalyst for producing synthesis gas and production of synthesis gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a catalyst having a small amount of carbon precipitated in a catalyst for producing a synthesis gas by oxidizing a lower hydrocarbon and to produce a synthesis gas by using the catalyst. SOLUTION: This catalyst for producing a synthesis gas by oxidizing the lower saturated hydrocarbon comprises the compound metal oxide containing the alkaline earth metal, titanium and nickel and having the atomic ratio of the alkaline earth metal and titanium of substantially 1/1 in which the alkaline earth metal and titanium form a perovskite-type oxide.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a synthetic gas (a mixed gas of carbon monoxide and hydrogen) by oxidizing a lower saturated hydrocarbon, especially methane, which is a main component of natural gas, and a method for use in the method. Regarding catalysts. More specifically, mixed gas of lower saturated hydrocarbon and oxygen at high temperature,
The present invention relates to a catalyst capable of suppressing the deposition of carbon on the catalyst and maintaining the activity for a long period of time when the synthesis gas is produced by being passed over the catalyst.

[0002]

2. Description of the Related Art A technology capable of efficiently producing an industrial raw material by chemical conversion from a lower saturated hydrocarbon, which is a main component of natural gas, which is difficult to industrially utilize due to its poor reactivity, is a petroleum-derived product. This is an extremely important technology because it enables the conversion of raw materials into natural gas.
The following three methods are mainly known as methods for oxidizing methane to convert it into a compound usable as a raw material for chemical industry. A method for producing ethane and ethylene by an oxidative coupling reaction by passing a mixed gas of methane and oxygen over a catalyst having a temperature of 700 ° C. or higher. Numerous types of catalysts have been found in the catalyst for this reaction, consisting of several combinations of metal oxides (Sokolovsky et al., Catal. Toda.
y, 14, 415 (1992)). However, it is difficult to increase the yields of ethane and ethylene, and the maximum yields of ethane and ethylene that have been obtained so far are about 25%, which has not reached the practical range. A method for producing methanol from a mixed gas of methane and oxygen. For example, pressure 50K
When a mixed gas is flowed under a reaction condition of g / cm 2 and a temperature of 350 ° C., a non-catalytic reaction proceeds and methanol is obtained in a yield of about 9% (Gesser et al., Appl. Catal., 5).
7, 45 (1990)). However, this method
Since it is carried out under pressure, there is a problem that it is extremely dangerous. In addition, the methanol yield is even lower in the atmospheric pressure catalytic reaction. A method for producing synthesis gas from a mixed gas of methane and steam, methane and carbon dioxide, and methane and oxygen.
Each of these reactions is represented by the formula below. CH ₄ + H ₂ O → CO + 3H ₂ (1) CH ₄ + CO ₂ → 2CO + 2H ₂ (2) CH ₄ + 1 / 2O ₂ → CO + 2H ₂ (3) The synthesis gas is used as a raw material for ammonia, methanol or acetic acid. Used for oil refining. Also, synthesis gas can be converted to gasoline by the Fischer-Tropsch method, and methanol can also be converted to gasoline by the mobile method.

Currently, the industrially practiced method for producing synthesis gas mainly relies on the steam reforming reaction of the above formula (1) which proceeds on an alumina-supported nickel catalyst. However, since this reaction is an endothermic reaction, a large amount of reaction heat must be supplied, which is a problem of an energy-consuming process. On the other hand, the reaction of the formula (3) is an exothermic reaction and therefore energy saving. This reaction proceeds without catalyst, but
A high reaction temperature of 0 ° C. or higher is required (edited by Oki et al., “Encyclopedia of Chemistry”, Tokyo Kagaku Dojin, Tokyo (1989)). It is known that when a catalyst is used in this reaction, the reaction proceeds even at a reaction temperature of 800 ° C. However, there is a problem that an expensive noble metal is necessary as an essential component of the catalyst (Claridge et al., Catal. Lett. , 22, 299 (199
3)). An inexpensive alumina-supported nickel catalyst is also effective in the reaction of the above formula (3), but there is a problem that it cannot be used for a long time because carbon is deposited on the catalyst and the activity is reduced (Claridge et al. Catal.Le
tt. , 22, 299 (1993)).

The present inventors have previously mentioned that the reaction catalyst in the above formula (3) consists of a mixed metal oxide of alkaline earth metal and titanium and nickel, and the atomic ratio of alkaline earth metal and titanium is 1 /. It has announced a catalyst that is 0.8 (C
atal. Lett. , 22 (1993) 307). This catalyst has a high activity for the oxidation reaction of hydrocarbons and, at the same time, C
Although it has a high selectivity to O and H ₂ , it was not yet satisfactory because of the large amount of carbon deposited.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a catalyst for producing a synthesis gas by the oxidation reaction of a lower hydrocarbon with a small amount of carbon deposition, and a method for producing a synthesis gas using the same. The task is to do.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, according to the present invention, in the method for producing a synthesis gas by the oxidation reaction of a lower saturated hydrocarbon, an alkaline earth metal, titanium and nickel are contained, and the atomic ratio of the alkaline earth metal and titanium is substantially 1 / 1, and a method for producing a synthesis gas is provided, characterized in that a catalyst comprising a mixed metal oxide in which the alkaline earth metal and titanium form a perovskite type oxide is used. Also,
According to the present invention, the alkaline earth metal, titanium and nickel are contained, the atomic ratio of the alkaline earth metal and titanium is substantially 1/1, and the alkaline earth metal and titanium are perovskite type. There is provided a catalyst for producing synthesis gas by the oxidation reaction of a lower saturated hydrocarbon, which is characterized by comprising a composite metal oxide forming an oxide.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the catalyst of the present invention comprising a mixed metal oxide containing an alkaline earth metal and titanium and nickel, the atomic ratio of the alkaline earth metal and titanium is substantially 1/1. Is required, which makes it possible to obtain a catalyst with reduced carbon deposition. Although the amount of nickel used is not particularly limited, it is usually 0.05 to 1, preferably 0.01 to 0.04 in terms of atomic ratio to titanium. Examples of the alkaline earth metal include magnesium, calcium, strontium, and barium. Preferred alkaline earth metals are strontium or calcium,
Or a combination thereof. In the catalyst of the present invention,
The alkaline earth metal and titanium form a perovskite type oxide (MTiO ₃ , M: alkaline earth metal), and nickel is present on the surface portion of the perovskite type oxide. The nickel in this case can be nickel oxide (NiO), but is preferably metallic nickel.

In order to preferably prepare the catalyst of the present invention, first, an alkaline earth metal, titanium and nickel are dissolved in an aqueous solution containing citric acid and ethylene glycol to prepare a solution, which is used as a stock solution. . A predetermined amount of these stock solutions is collected, mixed, and concentrated in a rotary evaporator while heating. Transfer the concentrate to a beaker and dry on a hot plate. This thing in air at 300 ℃
The organic substances are decomposed and scattered by heating to 500 ° C. and further baked at 500 ° C. to remove all the remaining organic substances. The solid obtained here is pulverized and then placed in an electric furnace again to obtain 85 in air.
Baking at 0 ° C. gives a composite metal oxide. Further, a perovskite type oxide composed of an alkaline earth metal and titanium is first prepared by the above procedure, and a predetermined amount of nickel stock solution is impregnated in the rotary evaporator, and then a catalyst is prepared by the same procedure as described above. X of these complex metal oxides
The line diffractogram shows a diffraction pattern assigned to a perovskite type oxide composed of an alkaline earth metal and titanium, and nickel oxide.

In the present invention, the composite metal oxide may be supported on an inorganic carrier to increase the contact area with the raw material mixed gas. Examples of the carrier include porous materials such as silica, alumina, titania and magnesia. The supporting method may be carried out by a kneading method or an impregnating method which is usually performed by using a mixed solution of a raw material stock solution of a composite metal oxide.

To produce synthesis gas using the catalyst of the present invention, a mixed gas of a lower hydrocarbon and oxygen or an oxygen-containing gas is brought into contact with the catalyst. In this case, it is preferable that the catalyst is reduced with methane or hydrogen before the mixed gas is brought into contact with the catalyst so that the nickel component on the catalyst is held in nickel in the metallic state in advance. The reduction of the nickel component can also be carried out by keeping the reaction temperature of the mixed gas at 750 ° C or higher and bringing it into contact with the catalyst. The synthetic gas production reaction of the present invention is represented by the following equation.

Embedded image (In the formula, m represents a number of 1 to 4)

The lower saturated hydrocarbon has 1 to 4 carbon atoms.
And methane, ethane, propane or butane. These lower saturated hydrocarbons are used alone or in the form of a mixture. Further, as the oxygen-containing gas, air, oxygen-enriched air, or the like can be used. . The proportion of oxygen used may be equal to or less than the theoretical amount, and for example, when the raw material hydrocarbon is methane, it is 0.4-
It is preferable to set it to about 0.5 mol. Reaction temperature is 650 to 1
The temperature is 500 ° C, preferably 750 to 1000 ° C. The reaction pressure may be normal pressure or increased pressure. As the reaction system, any system such as a fixed bed and a fluidized bed can be adopted.

[0012]

EXAMPLES The present invention will now be described in more detail by way of examples, which should not be construed as limiting the invention thereto.

Example 1 First, a stock solution of catalyst components was prepared by the following procedure. About 350 ml of 63 g of citric acid and 56 ml of ethylene glycol
10 g of calcium carbonate was gradually dissolved in this aqueous solution, and the total amount was adjusted to 500 ml with water to give a calcium stock solution. The strontium stock solution is also prepared by the same procedure as the above calcium stock solution, but 1
4.8 g was dissolved. 105 g of citric acid and 112 ml of ethylene glycol are dissolved in about 350 ml of water, and 28.4 g of tetraisopropyl orthotitanate is added to this aqueous solution. When the solution is vigorously stirred, the resulting white precipitate dissolves and becomes a clear solution. Add water to this to bring the total volume to 50.
The titanium stock solution was made up to 0 ml. 42 g citric acid
Dissolve 56 ml of ethylene glycol in about 250 ml of water, add 29.1 g of nickel nitrate hexahydrate, and stir at 90 ° C. in a rotary evaporator. A yellowish brown gas was generated after several hours, and when the generation of this gas stopped, water was added to the liquid to make the total volume 250 ml, and this was used as a nickel stock solution.

A catalyst was prepared from the thus obtained stock solution by the following procedure. 40 ml of calcium stock solution, 10 ml of strontium stock solution, 50 ml of titanium stock solution and 5 stock solutions of nickel
Mix ml, concentrate on a rotary evaporator and dry to dryness on a hot plate. This is put into an electric furnace and heated to 300 ° C. in air, and when the generation of white smoke is stopped, the temperature is raised to 500 ° C. and firing is performed for 5 hours. The solid obtained here is pulverized in a mortar and mixed well. The mixture was again baked in air at 850 ° C. for 10 hours, and the obtained composite metal oxide was used as a catalyst for the reaction. This composite metal oxide is represented by the following composition formula, and it was confirmed that the alkaline earth metal (Ca, Sr) and Ti form a perovskite type oxide. Ca _0.8 Sr _0.2 Ti _1.0 Ni _0.2 (5)

The reaction was carried out in a quartz reaction tube filled with 0.3 mg of catalyst in a methane flow rate of 1 liter / hour and an air flow rate of 2.4.
The temperature is raised while flowing a mixed gas of liter / hour to 800
The time when the temperature reached ℃ was taken as the start time of the reaction. Reaction start 20
The gas exiting the reaction tube after a lapse of time was collected and subjected to gas chromatography. The products were mostly carbon monoxide and hydrogen, others were small amounts of carbon dioxide and water. The reaction results were calculated from the results obtained in this analysis and are shown in Table 1. In the table, the selectivity of carbon monoxide was based on carbon, and the selectivity of hydrogen and the carbon balance were calculated from the following formulas.

(Equation 1)

(Equation 2)

Examples 2 to 3 Table 1 shows the results of reaction for 50 hours and 100 hours in the same manner as in Example 1.

Example 4 The results of reaction for 150 hours in the same manner as in Example 1 are shown in Table 1. After the reaction, the raw material gas was switched to nitrogen and the catalyst was cooled to room temperature, and then the nitrogen was switched to air again to raise the temperature at a rate of 2.5 ° C./min. Carbon dioxide in the reaction tube outlet gas was analyzed every 25 ° C., and the temperature was raised until the carbon dioxide was not detected. When the amount of carbon accumulated on the catalyst was calculated from this analysis result, 0.05% of carbon was accumulated per unit weight of the catalyst.

[0018]

[Table 1]

Example 5 First, 40 ml of the calcium stock solution, 10 ml of the strontium stock solution, and 50 ml of the titanium stock solution prepared in Example 1 were mixed to prepare a perovskite complex oxide in the same manner as in Example 1. Add 5 ml of nickel stock solution to this with water.
The solution diluted to ml was added, and the mixture was concentrated with a rotary evaporator. The procedure after drying on the hot plate is
An impregnated catalyst was prepared in the same manner as in Example 1. Using this catalyst, the reaction was carried out in the same manner as in Example 1. The reaction results are shown in Table 2.

Examples 6 to 7 Table 2 shows the results of reaction for 50 hours and 100 hours in the same manner as in Example 5.

Example 8 Table 2 shows the result of reaction for 150 hours in the same manner as in Example 1. When the amount of carbon accumulated on the catalyst after the reaction was measured by the same method as in Example 4, it was 0.1 per unit weight of the catalyst.
7% of carbon had accumulated.

[0022]

[Table 2]

Comparative Example 1 To 5.1 g of alumina was added a solution prepared by diluting 25 ml of the nickel stock solution prepared in Example 1 with water to 200 ml, and concentrated with a rotary evaporator. The impregnated catalyst was prepared in the same manner as in Example 1, except for the procedure after drying on a hot plate. Using this catalyst, the reaction was carried out in the same manner as in Example 1. Table 3 shows the reaction results.

Comparative Examples 2 to 3 Table 3 shows the results of reaction for 50 hours and 100 hours in the same manner as in Comparative Example 1.

Comparative Example 4 Table 2 shows the result of reaction for 150 hours in the same manner as in Comparative Example 1. When the amount of carbon accumulated on the catalyst after the reaction was measured by the same method as in Example 4, it was 29.
3% of carbon had accumulated.

[0026]

[Table 3]

Comparative Example 5 Calcium oxide (2.2 g), strontium oxide (1 g), titanium oxide (4 g) and nickel oxide (0.8 g) were thoroughly mixed in a mortar and then baked at 850 ° C. for 10 hours. The X-ray diffraction pattern of this composite oxide showed a pattern of a very weak perovskite type oxide and a complicated pattern belonging to the raw material oxide. When this was used and the reaction was carried out for 5 hours in the same manner as in Example 1, the methane conversion was 30.7%, the carbon monoxide selectivity was 4.8%, and the hydrogen selectivity was 9.8%. .

Comparative Example 6 In Example 5, the composition formula: Ca _0.8 Sr was used as the catalyst.
_{The same} experiment was conducted for 2 hours except that the composite metal oxide represented by _0.2 Ti _0.8 Ni _0.2 was used. In this case, 4.3% of carbon was accumulated per unit weight of catalyst.

[0029]

The present invention has the following features. (1) Energy can be reduced as compared with the steam reforming method. (2) Since the carbon deposition on the catalyst is suppressed, the catalytic activity is maintained for a long time. (3) The catalyst cost is low.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masao Shimizu 1-1 Higashi Tsukuba-shi, Ibaraki Institute of Industrial Science and Technology, Institute of Materials Engineering (72) Inventor Hideaki Harihara 1-1-chome, Tsukuba, Ibaraki Industrial Materials Institute of Engineering and Technology (72) Inventor Anfin Germund Andersen 1-1, Higashi 1-1 Tsukuba, Ibaraki Prefecture Institute of Industrial Science and Technology

Claims (2)

[Claims] 1. A method for producing a synthesis gas by an oxidation reaction of a lower saturated hydrocarbon, which contains an alkaline earth metal, titanium and nickel, and the atomic ratio of the alkaline earth metal and titanium is substantially 1/1. A method for producing synthesis gas, characterized in that a catalyst comprising a complex metal oxide in which the alkaline earth metal and titanium form a perovskite type oxide is used. 2. An alkaline earth metal, titanium and nickel are contained, the atomic ratio of the alkaline earth metal and titanium is substantially 1/1, and the alkaline earth metal and titanium are perovskite type oxides. A catalyst for producing synthesis gas by the oxidation reaction of lower saturated hydrocarbons, which is composed of a complex metal oxide forming a product.